I understand how you are using the term and that is why I posted all the definitions. So under your definition, a 61 note keyboard with the ability to layer two sounds would be unlimited polyphony if it could play 122 notes at one time. So in that case, both could be called unlimited, but I would argue that the Dexibell has a clear advantage.
Of course, a single keystrike can use more than one instance of polyphony (i.e. for stereo, crossfades, resonances). But let's put that aside and assume 1-to-1 note:polyphony. If 122 in the first instance and 320 in the Dexibell both let you play and sustain every single key of the keyboard with no dropouts no matter what available sound(s) are selected, than I'd say they are equivalent, and would disagree that Dexibell has a clear advantage, as there is no instance where there would be an audible benefit. (Well, apart from the benefit of having more than 61 keys to begin with.) But you make a good point about "unlimited polyphony" in a tone generator being a function of what a board could possibly ask of it. For example, the Dexibell supports a maximum of three parts. If they added a multi-timbral MIDI receive function (as many boards have, to allow them to do things like play multi-channel MIDI sequences that can serve as your background tracks), the same tone generator would no longer offer "unlimited" polyphony. Which ironically means that leaving a common feature out is how a board like this can claim unlimited polyphony, by simply not building in any way to use up more polyphony than the board is capable of.
Originally Posted By: Sam Mullins
Why not just say it has 320 and leave it at that?
I see why... because the 320 number alone doesn't communicate the benefit they're trying to sell, which is the claim that it it is impossible to play ever hear a dropped note. But yes, there is a hidden other side, which is that that is only true because it is impossible for the keyboard to split/layer (or MIDI-trigger) more than three sounds at once.